1. Field of the Invention
The present invention relates to a method of inserting supplementary information such as a secret mark into a digital signal.
It also relates to a method of extracting a secret mark inserted into a digital signal.
Correspondingly, the present invention relates to a device for inserting supplementary information and a device for extracting supplementary information, both suitable respectively for implementing the insertion and extraction methods according to the invention.
The digital signal considered in what follows will more particularly be a digital image signal.
The insertion and extraction methods in accordance with the invention fall within the technical field of marking (known as watermarking) of the digital data which can be interpreted as the insertion of a seal into the digital data, making it possible, for example, to authenticate the content of a digital data file. This marking is also called digital tattooing.
2. Related Art
Marking methods are known, for example from the document by F. Hartung and B. Girod, University of Erlangen-Nuremberg, “Watermarking of uncompressed and compressed video”, Signal Processing 66 (1998), pp 283-301, or else from the document U.S. Pat. No. 5,915,027.
However, none of these documents mentions the possibility of inserting a message the size of which is unknown when this message is extracted.